Method and system for transmission of seismic data

ABSTRACT

The transmission system combines a self-contained, wireless seismic acquistion unit and a wireless, line of site, communications unit to form a plurality of individual short-range transmission networks and also a mid-range, line of sight transmission network.

This application is a divisional of, and claims priority to, U.S. patentapplication Ser. No. 12/381,606, filed Mar. 13, 2009, which is acontinuation-in-part of, and claims priority to, U.S. patent applicationSer. No. 11/438,168 filed on May 22, 2006, now issued as U.S. Pat. No.7,983,847, which is a continuation application of, and claims priorityto, U.S. patent application Ser. No. 10/719,800, filed on Nov. 21, 2003,now issued as U.S. Pat. No. 7,124,028, all of which are incorporatedherein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to seismic data acquisition, and moreparticularly to a method and system for transmitting data and controlsignals between multiple remote stations in an array. Most particularly,the invention relates to a seismic data collection system utilizingmultiple, wireless, self-contained, seismic recording units or pods eachhaving an associated wireless communications unit in close, but detachedproximity thereto, the wireless communications unit having both shortrange and mid-range transmission capabilities.

2. Description of the Prior Art

Seismic exploration generally utilizes a seismic energy source togenerate an acoustic signal that propagates into the earth and ispartially reflected by subsurface seismic reflectors (i.e., interfacesbetween subsurface lithologic or fluid layers characterized by differentelastic properties). The reflected signals are detected and recorded byseismic units having receivers or geophones located at or near thesurface of the earth, thereby generating a seismic survey of thesubsurface. The recorded signals, or seismic energy data, can then beprocessed to yield information relating to the lithologic subsurfaceformations, identifying such features, as, for example, lithologicsubsurface formation boundaries.

Typically, the seismic units or stations are laid out in an array,wherein the array consists of a line of stations each having at leastone geophone attached thereto in order to record data from the seismiccross-section below the array. For data over a larger area and forthree-dimensional representations of a formation, multiple lines ofstations may be set out side-by-side, such that a grid of receivers isformed. Often, the stations and their geophones are remotely located orspread apart. In land seismic surveys for example, hundreds to thousandsof geophones may be deployed in a spatially diverse manner, such as atypical grid configuration where each line of stations extends for 5000meters with stations spaced every 25 meters and the successive stationlines are spaced 200 meters apart.

Various seismic data transmission systems are used to connect remoteseismic acquisition units to a control station. Generally, the seismicstations are controlled from a central location that transmits controlsignals to the stations and collects seismic and other data, such asquality control data, back from the stations. Alternatively, the seismicstations may transmit data back to an intermediate data collectionstation such as a concentrator, where the data is recorded and storeduntil retrieved. Whichever the case, the various stations are mostcommonly hard wired to one another utilizing data telemetry cable. Inthe case of systems deployed in a marine environment, such cabling maybe clad to withstand high pressure and corrosion. Commonly, cabletelemetry is used for data transmission between the individualreceivers, the stations and the central location. Other systems useon-board, wireless data transmission systems for communications and datatransmission. Still other systems temporarily store the data at eachstation until the data is extracted.

In the case of wired stations, typically several geophones are connectedin a parallel-series combination on a single twisted pair of wires toform a single receiver group or channel for a station. During the datacollection process, the output from each channel is digitized andrecorded by the station for subsequent analysis. In turn, stations areusually connected to cables used to communicate with and transport thecollected data to recorders located at either a control station or aconcentrator station.

In the case of wireless seismic units, each unit utilizes mid-range orlong range radio transmission to communicate with either a centralcontrol station or concentrator via a transmitter on-board the seismicunit. Transmissions are made either directly between a seismic unit andthe control station or directly between a seismic unit and theconcentrator. To the extent the transmissions are high power, long-rangesignals, such as between a seismic acquisition unit and a centralcontrol station, the transmissions generally require a license from thelocal governing authority. Units capable of such transmissions also havehigher power requirements and thus require larger battery packages. Tothe extent the seismic acquisition units transmit to a concentratorstation utilizing a low power, mid-range signal, the transmitting andreceiving units must typically have a line of site therebetween.

Those skilled in the art will understand that in order to enhancedetection of seismic energy within the earth, it is necessary tomaximize ground coupling between the earth and the seismic systems, andparticularly the geophones of the system. Thus, it is desirable toposition seismic units directly in contact with the ground andpreferably, maximize the surface area of contact between the seismicunit and the ground. Moreover, it is also desirable to minimize noisethat can arise from various external sources, such as wind, byminimizing the profile of the seismic unit, and specifically the heightof the seismic unit as it deployed on the ground. In this regard, evenan antenna projecting from the seismic unit will be subject tocross-winds and the like, thereby resulting in noise in the collectedseismic energy.

One drawback to low-profile seismic units placed on the ground is thattheir capability of wirelessly communicating with external systems isgreatly reduced, particularly if it is a line-of-sight system such asdescribed above. This is particularly true if the seismic unit is fullyor partially buried in the ground. In addition to the presence of aphysical structure in the line of site between the unit and a receiver,other factors that can inhibit transmissions are a weak signal, weatherconditions, topography, interference from other electrical devicesoperating in the vicinity of the unit, or disturbance of the unit'sdeployment position.

Thus, it would be desirable to provide a communication system for aseismic survey array that has flexibility in wirelessly transmittingsignals and data to and from remote seismic units and a control and/ordata collection station. The system should be capable of communicationbetween functional seismic units even if one or more intermediatestations fail to operate properly. In addition, the system should becapable of communication between functional seismic units even if achange in environmental or physical conditions inhibits or prevents adirect transmission between a remote unit and its control station. Thesystem should maximize wireless transmission capability while minimizingthe possibility of noise from external sources. Similarly, the systemshould maximize coupling between the system and the earth.

SUMMARY OF THE INVENTION

The present invention provides a system for collecting seismic datautilizing multiple, wireless, self-contained seismic data sensor units.Each individual seismic unit is self contained such that all of theelectronics are disposed within the case, including one or moregeophones, a power source, a local clock and a very short range wirelesstransmitter/receiver. In addition, associated with each individualseismic unit is a wireless communications unit in close proximity to,but decoupled from the seismic unit, the wireless communications unithaving a power source, a short range wireless transmitter/receiver forcommunicating with the seismic unit and a transmitter/receiver forcommunicating with other removed wireless systems.

Preferably, each seismic unit is disposed for burying just below thesurface of the ground. In this regard, each seismic unit may becylindrical in shape and the electronics for the seismic unit are housedin a sealed cylindrical package. Likewise, each wireless communicationsunit is disposed to be planted in the ground adjacent a seismic unit andproject up from the ground. Each wireless communications unit ispreferably formed of an elongated, rigid support structure such as apole, shaft or the like. A low power, short range wirelesstransmitter/receiver is carried on the structure. At a first end of thestructure is a spike or similar feature to permit the structure to bereadily and easily affixed to, “planted” in or otherwise secured to theground, while at a second end of the rigid structure is mounted a lowpower, mid-range, line of sight wireless transmitter/receiver. A powersource may likewise be carried on or otherwise associated with thesupport structure.

In another embodiment, a global positioning system unit is also carriedon the support structure, preferably at or near the second end.

In one embodiment of the invention, a single transceiver is utilized inplace of a separate transmitter and receiver set. Moreover multiple setsof transmitters and receivers for different range transmissions may bereplaced with a single transceiver with two power ranges. Such atransceiver may be utilized on the support structure rather thanseparate short range and mid-range transmitters/receivers, wherein afirst power setting permits the transceiver to be utilized as a shortrange device, and a second power setting permits the transceiver to beutilized as amid-range device.

The method according to the invention transmits radio signals betweenindividual seismic acquisition units in an array, such that thetransmissions can be passed in a relay chain through the array ofseismic units. The transmission between individual seismic units isenhanced by the wireless communications units of the invention.Preferably, each seismic unit is disposed in the ground so as to have avery low exposed profile. In one embodiment, each seismic unit is buriedin the ground several inches below the top soil so as to have no exposedprofile. A wireless communications unit is deployed in the groundadjacent each seismic unit, preferably a short distance away from theburied seismic unit. The wireless communications unit and the adjacentseismic unit communicate with one another utilizing the very short rangetransmission system. The wireless communications unit then communicateswith other wireless communications units, satellites or other wirelessreceivers utilizing longer, mid-range wireless radio transmissions. Theelongated length of the support structure permits the transceiver of thewireless communications unit to be raised above the ground to facilitatecommunicate with more remote wireless radio receivers, while the veryshort range transmission system permits communications between thewireless communications unit and the adjacent seismic unit.

Utilizing the seismic unit and wireless communications unit wirelesslycoupled to one another, multiple seismic acquisition units within thearray are capable of passing transmissions to multiple other seismicunits, even if the line of site on the ground between seismic units maybe inhibited. More specifically, any one seismic acquisitionunit/wireless communications unit in the array is capable oftransmitting radio signals to several other seismic acquisitionunit/wireless communications units positioned within the line of sight,radio range of the transmitting system. A network of radio-linkedseismic acquisition systems such as this permits data and control signaltransmission routes back to and from a control station to be varied asdesired or needed. In other words, the transmission path utilized totransmit data and control signals from and to the individual seismicacquisition systems (wherein a “system” is a single seismic acquisitionunit and associated wireless communications unit) in an array may bealtered. In transmissions up the chain, i.e., from the most remoteseismic acquisition system to the control station, each system receivesdata from a seismic system “down” the chain and transmits the receiveddata up the chain along with any data that may be locally stored on asystem. Preferably, as one or more transmissions move up one or morechains, it is bounced between seismic acquisition systems so as to berelayed by each system in the array. The specific transmission path,i.e., a particular “chain” of systems, for any given transmission mayvary between transmissions depending on overall requirements of thearray. Control signals, such as timing signals and the like, can bepassed back down the chain along the same or a different transmissionpath.

At least one and preferably a plurality of seismic acquisition systemsin the network are located in the proximity of the control station sothat the network can utilize mid-range radio frequency to transmitseismic data all the way back to the control station. In anotherembodiment of the invention, the control station is remotely locatedfrom the seismic systems and one or more concentrators are located inthe proximity of the seismic acquisition systems of the network so thatthe network can utilize mid-range radio frequency to transmit seismic/QCand other data to the concentrators. The concentrators, in-turn, canstore the data and/or transmit it back as desired to a control station.

Within the transmission network, there are multiple transmission pathsfrom the most remote seismic system to the control station/concentrator.The particular transmission path to be used for any given transmissionwill be determined based on the strength of the signal betweencommunicating antennas, the operational status of a seismic system andpath efficiency. In this regard, it should be noted that while a seismicunit forming part of a seismic system may not be operational, itsassociated wireless communications unit may still function as a waypoint for conveying a transmission along a path since the wirelesscommunications unit of a system operates under its own power separatefrom its associated seismic unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a seismic acquisition system contemplated bythe invention.

FIG. 2 is a top view of a seismic acquisition array illustratingpossible transmission paths between seismic acquisition unit strings inthe array.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the detailed description of the invention, like numerals are employedto designate like parts throughout. Various items of equipment, such asfasteners, fittings, etc., may be omitted to simplify the description.However, those skilled in the art will realize that such conventionalequipment can be employed as desired.

With reference to FIG. 1, there is shown a seismic data acquisitionsystem 10 comprised of a seismic data acquisition unit 12 and a lowpower, wireless communications unit 40. Seismic acquisition unit 12 isgenerally comprised of a case 14 in which is mounted a power source 16,a short-range transmitter 18, a short-range receiver 20 and at least onegeophone 22. Control electronics 24, which may include long term orshort term memory for storing seismic data and the like, may also beincluded in the case. Preferably, unit 12 is self-contained so that allelectrical components are disposed within case 14, requiring no externalwiring of any type. In this regard, seismic unit 12 is wirelessly linkedto wireless communications unit 40 via transmitter 18 and receiver 20.Notably, while the descriptions of preferred embodiments are intended todescribe a system where an external antenna is decoupled from theseismic unit 12, those skilled in the art will appreciate that seismicunit 12 may still include an internal antenna, such as may be providedfor operation in conjunction with a transmitter and/or receiver chipset, for short-range communications as described herein.

Wireless communications unit 40 generally comprises an elongated supportstructure 42 having a first end 44 and a second end 46. Mounted onsupport structure 42 are electrical components, including a power source48, a short-range transmitter 50 configured to wirelessly communicatewith the short-range receiver 20 within case 14, a short-range receiver52 configured to wirelessly communicate with the short-range transmitter18 within said case 14, a mid-range radio transmitter 54 and a mid-rangeradio receiver 56.

Preferably, case 14 is cylindrical in shape so that it can easily beburied in the ground as described below. Likewise, case 14 is preferablywater-tight. As such, while it is generally described for use on land,unit 14 may be deployed in wet environments and transition zoneenvironments.

Support structure 42 is preferable an elongated rod or pole. Disposed atthe first end 44 of support structure 42 is a mechanism 58 for engagingthe earth. Mechanism 58 may include, but is not limited to, a spike oran auger. In other embodiments, mechanism 58 may include a cylinder orother structure that mounts in the ground and is disposed for receipt ofend 44. In yet another embodiment, first end 44 of support structure 42may be configured to engage a stake placed in the ground, such as asurveyor's stake. It is common in the industry to deploy survey stakesover a proposed area for an array prior to deployment, therebyidentifying a general vicinity for deployment of a seismic unit 12. Byproviding a support structure 42 that can simply be engaged with apre-deployed surveyor's stake, the time required to deploy wirelessantenna 40 is reduced.

Support structure 42 may be solid, hollow or partially hollow. In onepreferred embodiment, support structure 42 is a pole with a portion thatis at least partially hollow for receipt of one or more of theelectrical components such that the electrical components are protectedfrom the outside environment. At the second end 46, support structure 42may include a mechanism 60 for manipulating support structure 42, suchas one or more grooves, apertures, threads or the like, therebypermitting one to manipulate support structure to permit mechanism 58 toengage the earth.

As described below, the respective mid-range transmitters/receivers ofeach wireless communications unit 40 communicate with each other basedon line-of-sight transmission. Thus, while no particular length forsupport structure 42 is required for the invention, the length ofsupport structure 42 should be of sufficient dimension to permitline-of-sight transmissions in the environment in which the wirelesscommunications units 40 are deployed. In one embodiment, supportstructure 42 is approximately 3-4 feet in length.

In one preferred embodiment, mid-range radio transmitter 54 and receiver56 are located adjacent second end 46, thereby enhancing transmissionrange when support structure 42 is engaged with the earth, whileshort-range transmitter 50 and receiver 52 are positioned nearer tofirst end 44, so as to be closer to the ground and closer to seismicunit 12.

One or more geophones 22 may be mounted in case 12. Geophones 22 may besingle component or multi-component, i.e., capable of obtaining seismicenergy in multiple axes. As used herein, the term geophone is used torefer to any device capable of detecting energy propagated through theearth, and may include, without limitation, traditional geophones,accelerometers, geophysical measuring transducers, MEMS, devices formeasuring geophysical properties, and the like.

Preferably, control electronics 24 include a processor, analog board andmemory. Memory may be long term, non-volatile in the event of powerloss, preferably of a size or capacity to record seismic data from aseries of seismic shoots over an extended period of time, such as daysor weeks.

As used herein, in one embodiment, “short-range” receivers,transmitters, transceivers and transmissions are used to refer toactivity in approximately the 2.4 GHz radio frequency band or otherwiseused in low power, wireless personal area networks (WPANs). Thoseskilled in the art will appreciate that frequencies in this generalrange are unlicensed and generally functional over short distances ofapproximately 50 feet or less. Frequency hopping spread spectrum radiotechnology is preferably utilized in one embodiment of the invention,and in particular, wireless protocols such as the non-limiting examplesof Bluetooth. In another embodiment of the invention, small, low-powerdigital radios based on the IEEE 802.15.4 standard for WPANs may beused, such as those based on the ZigBee standard. Systems based on theZigBee standard are desirable because they are targeted atradio-frequency (RF) applications that require a low data rate, longbattery life, and secure networking. The foregoing is preferred not onlybecause of its short distance functionality, but also because of its lowpower requirements. Notwithstanding the foregoing, other short distance,low power radio systems may also be employed, such as RFID systems.

In another embodiment of the invention, “short-range” receivers,transmitters, transceivers and transmissions are used to refer todevices that uses Long Wave (LW) magnetic signals to send and receiveshort (˜128 byte) data packets in a local regional network using IEEE1902.1 protocol commonly called RuBee. IEEE 1902.1 RuBee uses magneticwaves, also often called inductive communication, for transmission.Additionally, RuBee uses a low frequency (˜131 kHz) carrier. Althoughthis results in a comparatively slow (˜1,200 baud) transfer raterelative to other packet based network data standards, the ˜131 kHzoperating frequency provides RuBee with the advantages of ultra lowpower consumption (battery life measured in years), and normal operationnear steel and/or water, thereby permitting a seismic data acquisitionsystem as described herein to be deployed in costal transition zones andsimilar “wet” environments.

As used herein, “mid-range” receivers, transmitters and transmissionsare used to refer to activity in approximately the 2.4 GHz radiofrequency band operating under line-of-sight conditions forcommunicating units. Again, those skilled in the art will appreciatethat frequencies in this general range are unlicensed and functionalover distances of approximately one kilometer. Any standard mid-rangeradio transmission equipment may be utilized. One non-limiting examplebeing wireless fidelity (“Wi-Fi”) equipment, where transmissionparameters may be selected to provide signal carrier modulation schemessuch as complementary code keying (CCK)/packet binary convolution (PBCC)or direct sequence spread-spectrum (DSSS) or multi-carrier schemes suchas orthogonal frequency division multiplexing (OFDM) and code divisionmultiple access (CDMA).

While receivers and transmitters have been described separately herein,it will be appreciated that the foregoing may be combined in a singletransceiver as is well known in the industry. As such, any reference toa transmitter and receiver pair herein may be replaced by a transceiverin accordance with the descriptions herein.

Further, a receiver, transmitter or transceiver may be provided withadjustable power ranges for transmission, and as such, can be switchedbetween short-range transmission and mid-range transmission. In thisembodiment, for example, wireless communication unit 40 may be providedwith a single transceiver that can be toggled between a mid-range powersetting for communicating with other wireless communication units and alow-range power setting for communicating with a seismic unit 12wirelessly coupled to said communication unit 40.

Those skilled in the art will appreciate that the electricalrequirements of wireless communications unit 40, and in particular,WPANs operating under IEEE 802.15.4 or IEEE 1902.1 RuBee standard, aremuch less than seismic data acquisition unit 12, and as such, theoperation of wireless communications unit 40 can be accomplished withminimal power. For this reason, power source 48 may be physically verysmall. In one embodiment of the invention, power source 48 comprises oneor more 1.5 Volt (“Double AA”) batteries, a solar cell or the like.

Power savings can also be realized by placing the transmitters,receivers and/or transceivers in a low power or “sleep” mode duringperiods of inactivity. In one embodiment of the invention, it iscontemplated that a timing signal will periodically be broadcast out tothe seismic array over the mid-range network. A transceiver ismaintained in a low power state except during a time window in which thetiming signal is broadcast to the array. During this period or timewindow, the transceiver toggles to a higher power state in order toreceive the timing signal. Once the timing signal has been received viathe mid-range network by the wireless communication unit 40 andtransmitted to its associated seismic acquisition units 12 via theshort-range network, the transceiver can revert back to the low powerstate unil the time window for the next timing signal transmission.

Power source 48 may include a rechargeable battery. In such anembodiment, a charging system may be included as a component of powersource 48. Non-limiting examples of such a charging system includesystems capable of generating a charge based upon movement of thestructure on which the recharging system is mounted. Thus, in theinstant case, movement of the support structure 42 under wind or due toother vibrations, could be utilized to generate a power charge utilizingthe recharging system. Likewise a recharging system provided in aseismic unit 12 may utilize ground vibrations or seismic energy toeffectuate a charge.

Power source 16 for seismic unit 12 may be internally or externallymounted relative to case 14.

In another embodiment of the invention a global positioning system(“GPS”) receiver 55 is carried by support structure 42. Location andtiming information may then be conveyed to seismic unit 12 utilizing theshort-range transmission network. Other timing systems may likewise beincorporated as part of wireless communications unit 40 in order toprovide control signals, such as master timing signals, to seismic unit12 via the short-range network. Such timing signals may include aperiodic timing code, heartbeat or beacon signal transmitted over thenetwork of the system. Preferably, any of the foregoing timing systemsare low power in nature and capable of operating utilizing power source48.

The short range transmitters and receivers of each individual seismicdata acquisition system 10 form a short-range seismic data transmissionnetwork between an individual seismic data acquistion system 10 and anassociated wireless communications unit 40. Multiple seismic dataacquisition system 10 can be deployed in an array, such as is shown inFIG. 2. As such, the array 100 consists of a multiplicity of short-rangeseimsic data transmission networks as well as an overall mid-rangenetwork formed of the transmitters and receivers of said multipleseismic data acquisition systems 10.

During deployment, each seismic unit 12 is placed in contact with theground, forming a coupling therebetween so as to enhance seismic signaldetection. Likewise, each wireless communications unit 40 is secured tothe ground adjacent its respective seismic unit 12. Specifically, eachwireless communications unit 40 is vertically positioned so as toprotrude or project up from the ground, the unit 40 being fixed to theground by way of engagement mechanism 58. Preferably, wirelesscommunications unit 40 is placed sufficiently close to its seismic unit12 so as to permit short-range transmissions therebetween, but farenough removed from seismic unit 12 so as not to cause interference withthe operation of seismic unit 12. For example, such interference couldtake the form of movement of communications unit 40, such as by wind,that could result in the creation of unwanted seismic noise in thevicinity of the communications unit 40. In the preferred embodiment,wireless communications unit 40 is positioned within 2-5 feet of itsassociated seismic unit 12.

While seismic unit 12 may simply be placed on the ground, preferably itis partially or fully buried in the ground. Those skilled in the artwill appreciate that by burying seismic unit 12 in the ground, not onlyis coupling with the ground enhanced so as to yield a better fidelitysignal, but the profile of seismic unit 12 is reduced, therebyminimizing the potential for environmental interference with theoperation of seismic unit 12, such as noise from wind, rain ortampering. Preferably, seismic unit 12 is fully buried in the ground,with several inches of topsoil placed over it. The short-range wirelessnetworks disclosed herein will operate through the top soil. Soil typesand soil conditions dictate the depth a seismic unit 12 can be buriedand continue to communicate over the short-range network with itsassociated wireless communications unit 40. For example, it has beenfound that in wet sand, a unit 12 can be buried up to 12 inches belowthe surface and continue to maintain short-range contact. In eithercase, since seismic unit 12 has no external antenna, there is nothingprotruding from seismic unit 12 that could result in noise.

In one preferred embodiment, the case 14 of seismic unit 12 iscylindrical in shape so that seismic unit 12 can be readily buried inthe ground. A simple cylindrical hole need be dug in the groundutilizing any standard tool, such as an auger or a post-hole shovel.Those skilled in the art will appreciate that a round hole such as thisis the most expedient and simplest to dig, especially utilizing thestandard tools available, thereby reducing the labor necessary to deployseismic unit 12.

A wireless communications unit 40 and its adjacent seismic unit 12communicate with one another utilizing the very short range transmissionsystem described herein. The wireless communications unit 40 thencommunicates with other wireless communications units 40 via mid-range,line-of-sight radio transmissions. The elongated length of the supportstructure 42 of each wireless communications unit 40 permits themid-range transmitters and receivers to be raised above the surface ofthe ground to facilitate longer distance line-of-sight communicationswith other systems, while the very short range transmission systempermits communications between the wireless communications unit and theadjacent seismic unit.

In one preferred embodiment, the low power, wireless communicationsunits 40 permit the transmission of radio signals between individualseismic acquisition systems 10, i.e., a seismic acquisition unit 10 anda wireless communications unit 40, of an array, such that thetransmissions can be passed in a relay chain through the array utilizingthe wireless communications units 40. In other words, the transmissionbetween individual seismic systems 10 is enhanced by the wirelesscommunications units 40, while removing potential noise that istypically associated with antenna projecting from prior art seismicunits. In another embodiment, a plurality of wireless communicationsunits 40 can simply relay a signal without regard to, or even a needfor, an associated seismic acquisition unit 12.

In yet another embodiment of the invention, each individual seismic dataacquisition system 10 is comprised of a seismic data acquisition unit 12having a short-range receiver based on IEEE 1902.1 RuBee. The associatedwireless communication unit 40 is likewise provided with a short-rangetransmitter based on IEEE 1902.1 RuBee, along with a GPS. In thisembodiment, the wireless communication unit 40 does not include anymid-range or long range transmission equipment as described herein.Rather, a timing signal is received by the GPS directly from the GPSsatellite and is transmitted over the magnetic transmission network tothe seismic data acquisition unit 12. This permits the seismic dataacquisition unit 12 to be deployed in water or under a top layer of soilor under foliage or similar cover without sacrificing the ability tocommunicate with the GPS satellite, an ability that might otherwise beimpeded if the GPS were mounted in the seismic data acquisition unit 12itself. Further, such an arrangement permits the wireless communicationunit 40 to be physically decoupled from the seismic data acquisitionunit 12, thereby enjoying the benefits described herein.

As shown in FIG. 2, in the foregoing transmission method, a transmissionnetwork 100 is comprised of a plurality of seismic acquisition systems110 spread out in a seismic array 140 and controlled by control station160. Each acquisition system 110 is comprised of a seismic dataacquisition unit 10 and a low power, wireless communications unit 40.Array 140 is formed of multiple lines 180 of acquisition systems 110.Radio transmissions, and in particular, seismic data, quality controldata, timing signals and/or control signals, are passed from wirelesscommunications unit 40 to wireless communications unit 40 as thetransmission is bounced through the network 100 to or from controlstation 160. In one embodiment of network 100, concentrators 200 aredisposed between array 140 and control station 160. While the inventionwill be described in more detail with references to transmission oftiming signals out to the network from a control station 160, thoseskilled in the art will understand that the invention encompasses anytype of transmissions to or from a seismic unit, including, withoutlimitation, control transmissions, seismic data or quality control data.

With respect to the timing signal, it is contemplated that a timingsignal will be broadcast to the array periodically during time windowsso as to permit the seismic acquisition units 12 to be synchronized witha master clock. By utilizing such a synchronization method, low power,low cost, temperature compensated crystal oscillators can be utilized asthe local timing device in the individual seismic units 12, therebyreducing cost and power requirements for the seismic units 12.

Each wireless communications unit 40 preferably has an omnidirectionaltransmission range 220 and can form a wireless link 230 with multiplecommunications units 40. As shown, within the transmission range 220 ofa unit 40, there are multiple other communications units 40 capable ofreceiving the transmission, in essence forming a local area networkcomprised of mid-range wireless communications units 40. For example,unit 40 a has an omnidirectional transmission range 220 a. Fallingwithin the transmission range 220 a of communications unit 40 a arecommunications units 40 b-40 g. With the flexibility to transmit tomultiple communications units 40 each having the ability to receive andtransmit seismic data to multiple other communications units 40 withinthe array 140, each communications unit 40 within array 140 is presentedwith multiple paths for communicating seismic data back to controlstation 160. For example, communications unit 40′ can transmit seismicor QC data back to control station 160 by sending it along path 240,along path 250 or along some other path as determined by therequirements of network 100. Likewise, a timing signal can be sent alongthe same or different paths to communications unit 40′ from controlstation 160.

In another embodiment, a transmitting communications unit 40 may utilizedirectional transmitter such that transmissions are substantiallyunidirectional and made only to one or more communications units 40 in alimited direction. It is common in the art to utilize phased antennaarrays-an array consisting of two or more antenna to achievetransmission directionality and gain improvement. In these types ofantenna arrangements, various adjustable antenna parameters, such asphase, can be altered to control directionality and gain, and hence,transmission range. Thus, for purposes of this description,“unidirectional” means a transmission with a higher gain along one axisor in a limited direction, whereas “omni-directional” means atransmission with generally the same gain in substantially 360°. Thiswill maintain the flexibility to transmit to multiple communicationsunits in the direction the transmitting antenna is pointed, whilereducing the number of path options that need to be processed by theoverall system, thereby multiple paths to be transmitted on the samefrequency at the same time without interfering with one another. Inaddition, a higher gain in a single or limited direction can be achievedwithout the need for additional power, or alternatively, powerrequirements can be decreased, and thus battery life extended, whilemaintaining the same gain as an omnidirectional signal.

In the illustration of FIG. 2, array 140 is shown as being comprised ofthree seismic acquisition system strings 180 a, 180 b, and 180 c. Eachstring 180 a, 180 b, and 180 c illustrates a different potentialtransmission path defined by wireless links 230 between the wirelesscommunication units 40 within a string. Those skilled in the art willunderstand that the indicated wireless links 230 are for illustrativepurposes only and, for purposes of the invention, a “string” 180 ofseismic acquisition systems 110, and hence corresponding communicationsunits 40, for a particular transmission path is defined by the selectedtransmission path by which data is communicated from one unit 40 toanother. Thus, for any given array 140, a “string” of units may beconstantly changing between transmissions. Such an arrangement permitstransmissions to be rerouted in the event of some failure of a unit 40within the string. Likewise, transmissions can be rerouted in the eventof a weak signal between units 40 or to overcome topographic or otherobstacles that could interfere with short range, line of sitetransmissions. Furthermore, in addition some failure of a unit 40, itmay be desirable to reroute a transmission simply because of theoperational status of a unit. For example, a unit 40 with lower batterypower may be utilized downstream at the end of a string and avoided as atransmission relay further upstream in order to conserve the unit'sbatteries, i.e., upstream relay units require more power to relay thetransmission because of the cumulative size of the transmissions.

In the event multiple adjacent strings are desired, radio transmissionparameter assignments may be made to minimize interference with othertransmissions and permit reuse of the same transmission parameters. Forexample, string 180 a may transmit data at a first set of radiotransmission parameters while string 180 b may transmit data at a secondset of parameters. Since the transmissions from a sting 180 are shortrange, it may only be necessary for adjacent strings to utilizedifferent transmission parameters, depending on the array spread. Inthis regard, the physical seismic unit layout of a portion of array 140defined as a string 180 may be dependent on the mid-range transmissioncapabilities of the communications units 40 in the adjacent string.Non-adjacent strings utilizing the same string are sufficiently spacedapart so as not to interfered with one another. In other words, string180 b is defined such that its width is sufficient to ensure that anytransmission from an communications unit 40 from string 180 atransmitting with a certain set of radio transmission parameters willnot be received by any communications unit 40 from string 180 c set toreceive transmissions using the same set of radio transmissionparameters. Those skilled in the art will understand that there are manytransmission parameters that can be adjusted in this regard, includingthe non limiting examples of frequencies, time slots, power, methods ofmodulation, directional antenna gain, physical spacing of units andstrings, etc.

Furthermore, while three strings 180 are depicted to indicate possibletransmission paths, system 100 can comprise any number of strings. Thenumber of strings for any given group of transmissions is dependent onthe system requirements. For example, rather than multiple strings, eachcommunications unit 40 in an array 140 may be utilized in a singletransmission path such that the entire array 140 might be considered a“string” for purposes of the description. Those skilled in the art willunderstand that the number of transmission paths and the number ofacquisition units utilized for any given transmission may constantly beinflux to maximize the operation requirements for a particulartransmission or group of transmissions.

In one preferred embodiment, the transmitted signal strength of awireless communications unit 40 can be altered to adjust thetransmission range for a transmitting communications unit 40 such thatnumber of potential receiving communications units 40 can be controlled.In this regard, rather than utilizing multiple transmitter/receiverswithin an individual network for short and mid-range transmission,communications unit 40 may have a single transmitter/receiver that canbe toggled between a short-range transmission power and mid-rangetransmission power.

At least one and preferably a plurality of seismic acquisition systems110 in network 100 are proximately located to control station 160 sothat network 100 can utilize mid-range radio frequency to transmittiming signals from control station 160 to the seismic acquisitionsystems 110. Alternatively, data may be transmitted from the seismicacquisition systems 110 to control station 160. In one embodiment, aplurality of wireless communications units 40 can simply relay a signalto control station 160 without regard to, or even a need for, anassociated seismic acquisition unit 12. In another embodiment of theinvention, data is accumulated and stored at multiple, dispersedconcentrators 200 remote from control station 160. Concentrators 200 arelocated in the proximity, i.e., line-of-sight, of the communicationsunits 40 of the network 100 so that the network 100 can utilize lowpower, mid-range radio transmission to transmit data to theconcentrators 200. The concentrators 200, in-turn, can store the data ortransmit it back as desired to control station 160. In one embodiment,concentrators locally store seismic data but transmit quality controldata received from the acquisition units back to control station 160.Likewise, concentrators 200 may be used as way-points in thetransmission of control and timing signals out to the network 100.

Much like the individual communications units 40, each concentrator 200preferably also has a transmission range 260 that encompasses severalwireless communications units 40. As within the array 140, transmissionof data from a string 180 to the concentrator 200 may be made from aplurality of units 40. For example, concentrator 200 a has anomnidirectional transmission range 260 a. Falling within thetransmission range 260 a of concentrator 200 a are wirelesscommunications units 40 h-40 j. As such, any of wireless communicationsunits 40 h-40 j may transmit seismic data from string 180 a toconcentrator 200 a. Thus, a failure of one of the communications units,such as 40 h, would not prevent data from string 180 a from being passedup the line or communications signals from being passed down the line.Rather, the transmission path from string 180 a to concentrator 200 a,or vice-versa, would simply be rerouted through an operativecommunications unit, such as units 40 i or 40 j. Concentrators 200 mayalso be positioned so as to be within the mid-range transmissiondistance of adjacent concentrators.

As described above, network 100 can function either as a one-waynetwork, i.e., concentrators 200 are utilized only to receive datatransmitted from array 140 or concentrators 200 are used to transmit atiming or control signal out to array 140, or a two-way network, i.e.,concentrators 200 transmit command signals out to array 140 in additionto receiving data transmitted from array 140.

Transmissions to control station 160 from concentrators 200 orcommunications units 40 may also include GPS or other survey informationto establish the location of a particular unit 12 for purposes of theshot and for purposes of retrieval. This is particularly desirable forwireless units as described herein since it may be difficult to locatesuch units upon retrieval. GPS survey information may also be useful inselection of a transmission path within an array as described above.

In operation, a preferred transmission path may be preset in units 40 orpredetermined Likewise, alternate transmission paths may be preset inunits 40 or predetermined. These preset paths, as well as the number ofpaths required for a particular array 140, are determined based on thevolume of the data to be transmitted, the data transmission rates,signal strength and the number of “real time” radio channels havingdifferent transmission parameters such that the radio transmissionchannels are non-interfering, battery power, location of the unit, etc.

Prior to a transmission or a set of transmissions along a string, abeacon signal may be utilized to verify the preferred transmission pathin much the same way as an ad hoc network or peer to peer networkidentifies systems within the network. Alternatively, rather thantransmitting utilizing a preset or predetermined path, the beacon signalmay be used to establish a transmission path utilizing the abovedescribed parameters. If a beacon signal is transmitted and thepreferred transmission path is not available, system 100 will search foranother transmission path through the wireless communication units. Inone embodiment, the beacon signal is transmitted and the local wirelesscommunications units within range send a return signal acknowledgingtheir receipt of the beacon signal. Once a path is verified orestablished, as the case may be, the path may be “locked in” forpurposes of the particular transmission so that system 100 will notcontinue searching for another path. The beacon signal may be generatedfrom within the array 140 by the seismic unit systems themselves orinitiated by the control station or concentrator.

As mentioned above, one benefit of the invention is the ability toutilize flexible transmission paths that can be readily changed based onvarious internal and external parameters effecting the network. Thisflexability also renders the network itself much more reliable.Preferably, transmission paths can be established and/or reroutedon-the-fly based on these parameters. Another advantage of the system isthat it utilizes less power in transmitting a signal over a givendistance via multiple short transmissions than would be required of asingle transmission over the same distance. In other words, because thepower required to transmitt a signal decreases as one over the square ofthe transmission distance, it is much more optimal to transmit a signalin several short hops than it would be to transmit the same signal overthe same distance in a single hop. This is true even of low power,mid-range transmissions. Of course an additional advantage of the systemof the invention is that it may avoid the need to acquire high powerradio transmission licenses. Finally, unlike the prior art, the systemof the invention eliminates the need to physically locate a concentratoror similar device in the middle of a seismic array, nor utilize theconcentrator to sort and organize multiple seismic data transmissionsincoming directly from individual seismic acquisition systems.

Turning back to the individual seismic acquisition units as illustratedin FIG. 1, each seismic unit 12 is preferably wireless and requires noexternal cabling for data transmission, timing or unit control. Eachseismic unit 12 may contain a power source 16, such as a battery, ashort-range radio transmitter/receiver 18/20, control electronics, whichmay include, without limitation, a local clock, local memory for storingseismic data, and a processor housed within a casing 14. A geophonepackage 22 may be housed within the casing 14 or externally attachedthereto. Further, because the unit 12 need only transmit a short rangesignal, power requirements for the unit are minimized, in contrast tothe increased power requirements necessary to transmit a stronger signalto a more distant receiving device. By reducing the memory requirements,the transmission requirements and the battery requirements, the overallcost, as well as the physical size and weight, of each unit isminimized.

While certain features and embodiments of the invention have beendescribed in detail herein, it will be readily understood that theinvention encompasses all modifications and enhancements within thescope and spirit of the following claims.

1. A transmission method for seismic data acquisition units, said methodcomprising the steps of: A. Providing a self-contained wireless seismicacquistion unit, said unit comprising a casing; a power source for saidunit; a transceiver with short-range transmission capabilities disposedwithin said casing; and a geophone; B. Providing a wireless transmissioncommunications unit comprising an elongated support structure having afirst end and a second end; a power source for said communications unit;a transceiver with short-range transmission capabilities mounted on saidsupport structure and configured to wirelessly communicate with theshort-range transceiver within said casing; and a radio transceiver withmid-range transmission capabilities mounted on said support structure;C. Deploying said self-contained wireless seismic acquisition unit at adesired location in contact with the ground; D. Deploying saidcommunications unit adjacent to said seismic acquisition unit; E.Wirelessly coupling said seismic acquisition unit and saidcommunications unit to create a short-range transmission networktherebetween; F. Receiving a control signal over a mid-range radionetwork utilizing said mid-range radio transceiver mounted on saidsupport structure; and G. Transmitting the control signal between saidcommunications unit and said seismic unit utilizing said short-rangetransmission network.
 2. The method of claim 1, further comprising thesteps of: repeating steps A-F for at least three spaced apart seismicacquisition units and associated communications units deployed in anarray, wherein each of said communications units is capable of receivinga mid-range radio transmission and transmitting a mid-range radiotransmission; providing a transmission station for communicating via amid-range radio transmission with at least one communications unitwithin said array; subsequent to deployment, identifying at least twoseparate transmission paths between the transmission station and acommunications unit, wherein a transmission path is defined as a chainof at least two communications units and the transmission station, eachcapable of communicating in series via mid-range radio transmission;selecting a transmission path from among the identified transmissionpaths based on a set of transmission path criteria; and transmitting amid-range radio signal along said selected transmission path.
 3. Themethod of claim 1, further comprising the steps of: repeating steps A-Ffor a plurality of spaced apart seismic acquisition units and associatedwireless communications units deployed in an array, wherein each of saidwireless communications units is capable of receiving a mid-range radiotransmission and transmitting a mid-range radio transmission and whereineach of said seismic acquisition units is capable of acquiring seismicdata; utilizing at least two of said wireless communications units totransmit a control signal via mid-range radio transmission to anothercommunications unit in the array; utilizing at least two of saidwireless communications units to receive a control signal via mid-rangeradio transmission from another wireless communications unit in thearray; partitioning said plurality of wireless communications units andassociated seismic acquisition units into at least two sub-sets ofunits; and using a mid-range radio transmission technique havingparameters set so that non-interfering radio transmission may beeffected in each sub-set.
 4. The method of claim 1, wherein the step ofdeploying said self-contained wireless seismic acquisition unitcomprises at least partially burying said seismic acquisition unit inthe ground.
 5. The method of claim 1, wherein the step of deploying saidself-contained wireless seismic acquisition unit comprises burying saidseismic acquisition unit in the ground below the surface of the ground.6. The method of claim 1, wherein the step of deploying saidcommunications unit adjacent to said seismic acquisition unit comprisesthe step of engaging the first end of said elongated support structurewith the ground such that said support structure projects up from theground.
 7. The method of claim 1, wherein the step of deploying saidcommunications unit adjacent to said seismic acquisition unit comprisesthe step of engaging the first end of said elongated support structurewith the ground and orienting said support structure to be substantiallyvertical relative to the ground.
 8. The method of claim 2, furthercomprising the step of transmitting a first signal along onetransmission path and transmitting a second signal along the othertransmission path.
 9. The method of claim 1, wherein said control signalis a timing signal, said method further comprising the steps ofutilizing said control signal transmitted to the seismic unit todiscipline a local clock of said seismic unit based on a master controlclock.
 10. The method of claim 1, wherein said control signal is atiming signal, said method further comprising the steps of utilizingsaid control signal transmitted to the seismic unit to time stampseismic data acquired by said seismic unit.
 11. The method of claim 1,wherein the radio transceiver with mid-range transmission capabilityalso has short-range transmission capability.
 12. The method of claim11, said method further comprising the step of toggling the transceiverbetween mid-range transmission capability and short-range transmissioncapability.
 13. The method of claim 1, wherein at least two wirelesscommunication units fall within the mid-range radio transmission rangeof another wireless communication unit.
 14. The method of claim 1,wherein at least two seismic acquisition units fall within theshort-range transmission range of a wireless communication unit.
 15. Themethod of claim 7, wherein the radio transmission range of at least oneof the wireless communication units is omnidirectional.
 16. The methodof claim 7, wherein the radio transmission range of at least one of thewireless communication units is unidirectional.
 17. The method of claim1, further comprising the steps of: repeating steps A-F for a pluralityof spaced apart seismic acquisition units and associated communicationsunits deployed in an array, wherein each of said communications units iscapable of receiving a mid-range radio transmission and transmitting amid-range radio transmission; subsequent to deployment, identifying atleast two separate transmission paths from a first point to a secondpoint in the array from among the plurality of wireless communicationsunits, wherein a transmission path is defined as a chain of at leastthree communications units, each capable of communicating in series viamid-range radio transmission; selecting a transmission path from amongthe identified transmission paths based on a set of transmission pathcriteria; and transmitting a mid-range radio signal along said selectedtransmission path.
 18. The method of claim 17, wherein said transmissionchains include each wireless communication unit in the array.
 19. Themethod of claim 1, further comprising the step of adjusting thetransmission range of a wireless communication unit so as to alter thenumber of other wireless communication units within radio transmissionrange of the adjusted wireless communication unit.
 20. The method ofclaim 2, wherein said transmission station is within mid-range radiorange of at least two wireless communication units.
 21. The method ofclaim 2, wherein said transmission station is within mid-range radiorange of at least three wireless communication units.
 22. The method ofclaim 2, wherein a transmission station receives seismic data from saidseismic acquisition units and said seismic data is transmitted over thesame transmission chain utilized to transmit control signals to saidseismic acquisition units from the transmission station.
 23. The methodof claim 2, wherein a transmission station receives seismic data fromsaid seismic acquisition units and said seismic data is transmitted overa different transmission chain than that utilized to transmit controlsignals to said seismic acquisition units from the transmission station.24. The method of claim 2, wherein the transmissions between saidseismic acquisition units and the transmission station are madeutilizing different transmission chains.
 25. The method of claim 1,further comprising the steps of transmitting quality control data from aseismic acquisition unit to its associated wireless communication unitover the short-range network established therebetween and subsequentlytransmitting said quality control data from the wireless communicationunit to another wireless communication unit over the mid-range networkestablished between a plurality of wireless communication units in thearray.
 26. The method of claim 2, wherein said transmission path ispreset among the wireless communication units.
 27. The method of claim26, wherein a second alternate transmission path is preset among thewireless communication units.
 28. The method of claim 2, whereinmultiple transmission paths are identified.
 29. The method of claim 28,further comprising the step of selecting a transmission path among themultiple transmission paths prior to transmitting.
 30. The method ofclaim 1, further comprising the step of determining the number of otherwireless communication units within mid-range transmission range of awireless communication unit.
 31. The method of claim 1, furthercomprising the step of determining the signal strength for otherwireless communication units within transmission range of a wirelesscommunication unit.
 32. The method of claim 2, further comprising thestep of generating a beacon signal and transmitting the beacon signalalong the transmission path.
 33. The method of claim 2, furthercomprising the step of verifying the transmission path by generating abeacon signal.
 34. The method of claim 32, further comprising the stepof utilizing said beacon signal to establish a synchronized recordingtime among the seismic acquisition units.
 35. The method of claim 32,further comprising the step of simultaneously initiating recording ofseismic data by said seismic acquisition units.
 36. The method of claim22, wherein seismic data transmitted from a seismic acquisition unit istime stamped prior to transmission.
 37. The method of claim 1, whereinsaid short-range transmission network utilizes IEEE 1902.1 protocol. 38.The method of claim 1, wherein said short-range transmission networkoperates in the 2.4 GHz radio frequency band.
 39. The method of claim 9,wherein said step of disciplining is repeated on a period basis as theseismic unit is acquiring seismic data.
 40. The method of claim 10,wherein said step of time stamping is repeated on a period basis as theseismic unit is acquiring seismic data.
 41. A method for transmission ofcontrol signals among an array of seismic data acquision units, saidmethod comprising the steps of: A. Establishing a plurality ofshort-range transmission networks within a seismic data acquistion unitarray, wherein each short-range transmission network is comprised of aself-contained wireless seismic acquistion unit having a casing; a powersource for said unit; a short-range radio transmission transceiverdisposed within said casing; and a geophone disposed within said casingand a wireless communication unit positioned in close proximity to saidseismic data acquisition unit, said wireless communication unit havingan elongated support structure; a power source for said communicationsunit separate from said acquisition unit; a radio transceiver mounted onsaid support structure and configured in a first state to wirelesslycommunicate with the short-range radio transceiver within said casing;said transceiver further configured in a second state to transmit andreceive mid-range radio transmissions; B. Transmitting a timing signalbetween a plurality of mid-range radio transceivers each mounted on asupport structure via a mid-range radio network; and C. Transmitting thetiming signal to a seismic unit from a wireless communication unit viathe short-range transmission network.
 42. A transmission method forseismic data acquisition units, said method comprising the steps of: A.Deploying a plurality of seismic acquistion unit; B. Deploying aplurality of wireless transmission communication units; C. Establishinga wireless magnetic transmission network between a communication unitand an acquisition unit utilizing Long Wave (LW) magnetic signals; andD. Establishing a wireless radio transmission network between at leasttwo communication units utilizing radio signals.
 43. The method of claim42, further comprising the steps of A. Utilizing a communication unit toreceive a timing signal over a radio transmission network; and B.Transmitting the received timing signal over the magnetic transmissionnetwork to a seismic acquisition unit.
 44. A timing signal conditioningmethod for seismic data acquisition units, said method comprising thesteps of: A. Deploying a plurality of seismic acquistion unit; B.Deploying a plurality of wireless transmission communication units; C.Establishing a wireless magnetic transmission network between acommunication unit and an acquisition unit utilizing Long Wave (LW)magnetic signals; D. Utilizing a wireless transmission communicationunit to receive a timing signal from a GPS satellite; and E.Transmitting said GPS timing signal to a seismic acquisition unitutilizing said wireless magnetic transmission network.